application.conf

play {
  modules {
    disabled += "play.api.libs.mailer.SMTPConfigurationModule"
    enabled += "controllers.CustomMailerConfigurationModule"
  }
}

CustomSMTPConfigurationProvider.scala

class CustomSMTPConfigurationProvider extends Provider[SMTPConfiguration] {
  override def get() = new SMTPConfiguration("typesafe.org", 1234)
}

class CustomMailerConfigurationModule extends Module {
  def bindings(environment: Environment, configuration: Configuration) = Seq(
    bind[SMTPConfiguration].toProvider[CustomSMTPConfigurationProvider]
  )
}

ImmutableConfigure.scala

class ImmutableConfigure @Inject()(mailer: MailerClient) {

  def send() {
    val mailer = new SMTPMailer(SMTPConfiguration("typesafe.org", 1234))
    val id = mailer.send(Email("Simple email", "Mister FROM <[email protected]>"))
  }
}

MutableConfigure.scala

class MutableConfigure @Inject()(mailer: MailerClient) {

  def send() {
    val email = Email("Simple email", "[email protected]", Seq("[email protected]"))
    val id = mailer.configure(Configuration.from(Map("host" -> "typesafe.org", "port" -> 1234))).send(email)
  }
}